1. Field of the Invention
This invention relates to a medium for electrophoresis in the form of an aqueous gel suitably employable for electrophoresis of biopolymers such as proteins, and more particularly relates to an aqueous polyacrylamide gel medium for electrophoresis which can be prepared in the presence of oxygen.
2. Description of Prior Arts
The electrophoresis can be carried out in the following manner: a membrane medium for electrophoresis prepared by coating or casting a membrane-forming material such as agar, cellulose, cellulose acetate, starch, silica gel or polyacrylamide gel over a support such as a glass plate or transparent plastic sheet (or film) is impregnated with a buffer solution; on the medium is applied a substance to be analyzed (sample); the applied sample is developed (or resolved) on or in the medium by applying a voltage between the both ends of the support and dyed thereon; and then the dyed sample is measured on the optical density to quantitatively determine the components of the sample.
Details of the electrophoresis and medium therefor are given in "Experimental Text for Electrophoresis (5th revision)" editted by Electrophoresis Society of Japan (Bunkodo, 1975), "Modern Electrophoresis" editted by Aoki & Nagai (Hirokawa Shoten, 1973), etc.
Recently, the electrophoresis has been employed to analyze substances originating from a living body; for instance, the analyses of proteins originating from a living body are generally performed in the course of biochemical analysis for diagnosis.
As the membrane or sheet for electrophoresis, a filter paper was previously employed, but recently an agarose membrane or a polyacrylamide gel membrane (or medium) has been employed from the viewpoints of their advantageous properties. Particularly, the polyacrylamide gel membrane showing melecular sieve function is widely employed recently. The polyacrylamide gel membrane can be prepared by crosslinking polymerization of a monomer such as acrylamide and a two-functional cross-linking agent such as N,N'-methylenebisacrylamide under an oxygen-free condition in the presence of water and a polymerization catalyst.
Since the polymerization reaction for the preparation of polyacrylamide is a radical crosslinking polymerization as described above, the polymerization can be easily inhibited by the presence of oxygen. Therefore, the gel membrane should be prepared in the absence of oxygen. For this reason, a polyacrylamide gel membrane is generally prepared by a process involving: introducing an aqueous solution (gel-forming solution or gel solution) containing acrylamide, a crosslinking agent and a polymerization catalyst into a cell formed between two glass plates with a certain clearance (e.g., 0.3-1 mm); sealing the gel-forming solution from oxygen; and causing the crosslinking polymerization to prepare the desired gel membrane.
The prepared polyacrylamide gel is horizontally or vertically placed for performing slab electrophoresis. The electrophoresis is performed for a certain period of time under predetermined conditions, and the desired analysis of the components originating from the living body is done after dyeing the electrophoresed gel membrane with Ponceau 3R (Ciba-Geigy), Coomassie Brilliant Blue G-250 (ICI), silver, etc.
As described above, the requirement of oxygen-free conditions for the preparation of the conventional polyacrylamide gel is one reason to make it difficult to prepare the polyacrylamide gel membrane (medium) in a mass scale.